how to make camera look through objects from only one side?
Final result:

This is kinda same idea as @Duarte Farrajota Ramos but it is working in Cycles (viewport/camera).



Mesh:

Your mesh normals should point to the inside of the room as in the image below.



Materials:

You will need to assign different materials for floor and walls and ceiling.



Floor material. Could be anything you want.

Wall and ceiling material. Should look like this and in the place of red Diffuse you can and anything you want. Remember to check if Transparent shader color is pure white. Hex value #FFFFFF.